Protecting speech privacy has become an increasingly important task in modern workplaces. Those who speak would like the content of their speech to be confined to their offices or conference rooms. Unintended listeners, on the other hand, would like not to be disturbed by the unnecessary oral information. Irritating speech from others is also problematic in settings other than offices including, for example, homes, libraries, banks, and/or the like, e.g., where people are often unaware that their speech is disturbing to others.
In fact, there are a number of potential adverse effects elicited by enduring annoying sounds. These adverse effects can range from productivity losses for organizations (e.g., for failure to maintain, and/or interruptions in, concentration) to medical issues for people (e.g., the onset of headaches caused by annoying sounds, irritability, increased heart rate, and/or the like) and even to the urge to seek a new work environment. Misophonia, a learned condition relating to the association of sound with something unpleasant, also happens from time-to-time. Some people suffer from acoustic hyper-vigilance or oversensitivity to certain sounds and intruding speech.
In many settings, sound annoyance oftentimes is related to loudness, abruptness, high pitch and, in the case of speech sounds, the speech content. In many cases, there are certain components in speech or noise that make them particularly disruptive or irritating. With respect to speech content, humans tend, regardless of the volume, to strain to hear what is said, which has been found to subconsciously add to the annoyance. That is, once one is aware of somebody speaking, one oftentimes becomes involuntarily involved, adding a sort of subconscious annoyance.
People oftentimes are irritated by high frequencies (e.g., sounds in the 2,000-4,000 Hz range). These sounds do not need to be of high intensity to be perceived to be loud. In this regard, FIG. 1 is a graph showing perceived human hearing at a constant level, plotting sound pressure level against frequency. As can be seen, the “equal loudness sound curve” in FIG. 1 demonstrates that lower-frequency sounds with high sound pressure levels generally are perceived the same way as higher-frequency sounds with lower sound pressure levels. Typically, irritation increases with volume of the noise.
Sound waves, including speech, propagate primarily in a longitudinal way, by alternating compressions and rarefactions of air. When the waves hit a wall, the distortion of molecules creates pressure on the outside of the wall that, in turn, emanates secondary sound.
It will be appreciated that it would be desirable to design a wall with noise-cancellation, including speech-disrupting properties, for at least some settings. Some construction materials, including glass, are poor sound insulators. At the same time, use of glass is often advantageous, as it provides an excellent visual connectivity between offices and can contribute to the engagement of employees. Thus, it will be appreciated that it would be desirable to design an optically transparent wall with noise-cancellation properties, including speech disrupting properties, for at least some of these settings.
Sound-insulating windows have been known in the art. One mainstream approach involves increasing the Sound Transmission Class (STC) of the wall. STC is an integer rating of how well a wall attenuates sound. It is weighted over 16 frequencies across the range of human hearing. STC can be increased, for example, by using certain spacing in connection with double-pane glass walls in order to destructively resonate sound; increasing the STC of single- or double-pane walls by increasing thickness of the glass, and/or using laminated glass.
Unfortunately, however, these techniques come at a cost. For example, increasing the thickness of single-pane glass allows only modest sound abatement, while adding to the cost. The use of double-pane glass, albeit more effective, typically requires the use of at least two comparatively thick (e.g., 6-12.5 mm) glass sheets. These approaches also typically require high tolerances in the wall construction, and the use of special pliant mechanical connections in order to avoid flanking effects. Glass of such thickness is heavy and expensive, and results in a high installation cost.
Furthermore, double-pane walls typically work well primarily for low-frequency sounds. This can limit their effectiveness to a smaller number of applications such as, for example, to exterior walls to counteract the low-frequency noise of jet and car engines, noise of seaports, railways, etc. At the same time, most speech sounds responsible for both annoyance and speech recognition lie within the 1800+ Hz range. It therefore would be desirable to achieve noise cancellation in this higher-frequency range, e.g., in order to help block irritating components and increase speech privacy.
Instead of abating higher-frequency noise, some acoustical solutions focus on sound masking. For instance, sounds of various frequencies may be electronically overlapped through a speaker, so that the extra sound is provided “on top of” the original noise. Sound masking can include Nature sounds ranging from waterfall and rain sounds to fire crackling and thunderstorm sounds. Various types of artificially-generated masking noises such as, for example, white, pink, brown, and other noises, also are used in this regard. A main purpose of these sound-masking techniques involves reducing annoyance of the surrounding noises, and such approaches can indeed obscure the irritation. Unfortunately, however, it also creates additional noise, which some people perceive as irritating in itself. One problem of the above-mentioned sound masking techniques is that their frequencies lie outside the range of frequency of appearance of syllables—the building blocks of speech. See, for example, FIG. 11, discussed in greater detail below, which shows the results of temporal frequency analysis of a normal speech pattern, white noise, and some of Nature's sounds maskers.
Still another example approach for achieving noise cancellation is used in Bose headphones. This approach involves registering incoming noise and creating a counteracting noise that is out of phase with the registered incoming noise. Although it is relatively easy for one to isolate oneself from the environment by wearing headphones, doing so does not prevent the person wearing the headphones from making noises that others find disturbing. That is, even though the person wearing the headphones might have created an isolating environment on an individual level, there is still an issue in creating an isolation area for a group such that others in the group cannot hear what is being said. Additionally, one difficulty of this concept for walls is that it typically only works well on a small area and is suitable primarily for continuous low-frequency sounds (such as, for example, the hum of engines). One reason for this is that only a narrow band of frequencies can be effectively tuned out of phase, and the higher the frequencies, the smaller the aural space of the effective noise cancellation would be.
Thus, it will be appreciated that it would be desirable to provide for techniques that overcome some or all of the above-described and/or other speech-masking problems. For example, it will be appreciated that it would be desirable to provide acoustic techniques that help reduce or otherwise compensate for sounds, including speech, that cause irritation and annoyance to people.
The inventor has recognized that it would be desirable to block the content of the speech from being understood by people around the person speaking in environments such as, for example, open or enclosed office spaces and/or other environments, adjacent offices separated by thin walls with low STC, vehicles (including, for example, commercial and private vehicles such as cars, trucks, trains, airplanes, etc.), bank teller spaces, hospitals, police stations, conference rooms, etc. Indeed, there seemingly is an ever-increasing demand in acoustic privacy, broadly speaking, in modern office spaces.
Current techniques, including the sound-masking and sound-cancelling techniques discussed above, do not target the content of the speech, and are not specifically speech intelligibility disrupting technologies. In fact, noise masking techniques know in the art are, in a fundamental way, not intended to effectively disrupt speech without causing a great deal of additional annoyance. In this regard, the inventor has realized that although the fundamental frequencies of human speech do lie in the same frequency spectrum as some of the available masking noises and/or ranges that can be at least partially cancelled, information-containing blocks have been found to appear at the essentially different frequencies. Information-containing blocks in this context are formants, which represent the energy bursts of sound.
It thus has been recognized that it would be desirable to develop an acoustic-masking technique directed to disrupting the informational content of the speech without causing an additional annoyance. It will be appreciated that masking techniques generally add a certain amount of loudness on top of the original speech. The techniques of certain example embodiments add only a small amount of additional loudness, e.g., because they specifically target essentials cues of speech, such as formants.
In certain example embodiments, a method for disrupting speech intelligibility is provided. The method includes: receiving, via a microphone, an original speech signal; generating an intelligibility-disrupting masking signal from the original speech signal, the intelligibility-disrupting masking signal being different from the original speech signal by virtue of being generated to have (a) a time delay relative to the original speech signal, (b) the time delay changing according to an oscillation frequency, and (c) an amplitude that is modulated; and causing the intelligibility-disrupting masking signal to be outputted through a speaker to reduce the level of intelligibility of the original speech signal.
Devices and systems incorporating such functionality also contemplated herein, as are walls incorporating such devices and systems.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.